1. Field of the Invention
The present invention applies to the field of On-Line Analytical Processing (OLAP); and specifically, to the field of On-Line Analytical Processing that accesses relational databases.
2. Discussion of the Related Art
A significant advantage of an OLAP data source is that the data are organized in an understandable manner for the end user. The physical representation of the data is separated from the semantic layer presented to the end user. It can be very useful to help the end user to define this kind on layer on top of any type of data source. An ideal tool takes any heterogonous data source and displays the data in a unified semantic layer.
You can see each hierarchy that composes a dimension one different dimension by hierarchy.
According to the present invention, it is possible to map all relational models to OLAP models. The process is highly automated according to the present invention.
An OLAP data source is a database like a RDBMS. The OLAP model is similar to a data warehouse. It is composed of one or more fact table (multi-cube versus hypercube) and dimensions table links this fact table. In the OLAP model, you do not see the key and relation, only the useful object. The object is typed (dimension, measure, member) and presented in an organized manner. An OLAP data source use important abstraction between the data storage and the data representation.
Two differences between an OLAP data source and a RDBMS are evident: namely the speed and the capacity to perform complex calculations.
There is need to leverage the gap between the data sources capabilities to offer a generic query tool that is not dependent of the data source. A difference between the two models is the complex calculations such as row based calculations in the OLAP model. The row base calculations are possible, but very complicated with a RDBMS and the SQL language.
A foreign key is an attribute (or attribute combination) in one relation R2 whose values are required to match those of the primary key of some relation R1 (R1 and R2 not necessarily distinct).